Funds are requested to purchase a Flow Cytometer/Cell Sorter for at least six groups of investigators in the Department of Pathology of the College of Medicine of the University of Florida. The scope of these investigations is very broad and includes: a) analyses of surface antigens, DNA content and kinetic properties of human and murine lymphoma cells, b) detection and quantitation of lymphocyte antigens in prediabetes and endocrine diseases, c) detection of anti-HLA antibodies on human T- lymphocytes and platelets, d) identification of cell surface markers identifying metastic phenotypes and, e) identification and quantitation of Class II molecules on murine splenic B lymphocytes. Although a flow cytometer/cell sorter already exists in our department and is available for these projects, the instrument is reaching obsolescence and is heavily committed to analysis of high priority, hospital-related clinical samples. The lack of ready access to a modern and reliable instrument and a faster, high performance computer is jeopardizing the current efforts of these investigators and those of other researchers with increasing needs for flow cytometry and cell sorting. We have extensive experience with this technology and with the organization and planning of a multi-user laboratory. We also have competent personnel to operate and maintain the instruments. The commitments of the College of Medicine and the Department of Pathology to support our efforts, and the number of well funded projects that require this technology, insure the proper functioning and adequate future operation of the flow cytometry/sorting facility.